Sony has launched the opening salvo in the online gaming war with the release of an internet adpater for its Playstation 2 console.

PS2 gamers in North America can now battle each other over the internet.

An online adapter for Sony's best-selling console has gone on sale for $39.99 which allows a PS2 to connect to the internet over a dial-up or high-speed broadband connection.

Online gaming has the potential to transform the economics of the computer gaming industry, say experts, with one-third of frequent gamer playing over the internet.

Hardcore gamers

At launch a total of 13 multi-player games will be available to play online on the PS2.

Madden NFL 2003: One of 13 games online

They include the military shooter Socom: US Navy Seals, the skate boarding game Tony Hawk's Pro Skater 4 and the American football game Madden NFL 2003.

Sony is hoping to sell 400,000 adapters by the end of the year, a small percentage of the 11 million consoles in American homes.

The Japanese electronics giant is targeting hardcore gamers, who spend almost $100 a month on games according to a recent survey.

"The most important thing is, first of all, that we let the core gamers know we are taking the PS2 experience into an online environment," said Kaz Hirai, president of Sony Computer Entertainment of America.

"If you know you're good, instead of beating up your friends all the time you can go out into the network and compete with others who are just as cocky as you are," he said.

Online arena

Sony's biggest potential competitor for online gaming is the Xbox Live service from Microsoft that is due to be launched on 15 November.

Gamers will have to pay $49.95 a year to play over the Xbox network, built and run by Microsoft.

Nintendo's online plans are still unclear. It has said it will bring out network adapters this year for its GameCube console but has not provided additional information.

Few analysts expect online gaming via consoles to attract a large following until the next generation of internet-ready consoles become available.